Zenith INAT 35/40 Idle Troubles

[Gotha]

I have a 1975 Mercedes Benz 230.6, W114.015 chassis with the M180 engine and a manual, 4 speed G735 trans. The car will not hold a normal idle. It will will occasionally hold a very low, 300-400 rpm idle. I have rebuilt the carbs completely with new complete kits. This includes the spacers underneath the carbs, secondary bellows, mixture screws etc. I have checked the resistance on the ignition wires and coil and everything is correct. There is also new plugs, cap and rotor. The timing is also correct. I have replaced the fuel pump, hoses and the fuel tank screen. The engine has about 80,000 miles on it. When the car does idle and I try to adjust the idle screws they make no increase in rpm. The mixture screws seem to make little difference also. I can increase revs with the linkage but then the engine dies. It will sometimes also spit back through the carbs. I have tried to adjust everything as suggested in previous posts and through the manual but, I am almost at the end of my patience. Does anyone have any suggestions? Please Help.

Regards,
Gotha

[flacollect]

Wow, sounds exactly like what mine was doing. I was getting too much fuel from the float level. It was set at 20mm. I set it to 28mm and it seemed to lean it out where it doesn't foul plugs. However, the diaphram on the choke has to be set correctly or it won't idle as well.
I am in the process of cleaning my tank, but it sounds like you did all of that already. I certainly hope someone can help you on this because these carbs can be a world of trouble. Good luck.

zenith 35/40

1967 250s

[mak]

[. I have tried to adjust everything as suggested in previous posts and through the manual but, I am almost at the end of my patience. Does anyone have any suggestions? Please Help.

Regards,
Gotha [/QUOTE]

[I][/I

Does closing the air intake on top on the carb help ,indicating a lean condition.?

remove both the idle mixture screws and generously squirt carb cleaner into the screw. bore. next repeat this for the idle air intake .This will be a very small hole near the center area .under it located would be the brass idle tube . this will clear out the idle system .install the idle mixture screws and test.I hope it will help

regards
mak

[Gotha]

Firstly,
Thanks for the advice. I tried shooting some carb cleaner into the mixture openings and one was apparently not clear. The car seems to want to idle but only does so briefly. I also noticed a little bit of wetness, under the carbs, around the bottom of the upper spacer and the heat shield. I have read where these parts can warp and cause problems. I tried tightening the carb to manifold bolts and it seems to have helped a little bit more but, it is still moist and not wanting to idle. I suppose my next move is to remove the carbs, check the surfaces for being level and either lightly sand or try the double gasket approach. Anyone else have other suggestions? Will a fuel resistant gasket maker be a good idea if applied lightly? Is this the real reason for my not being able to hold and idle?

Many Thanks,
Gotha

[ctaylor738]

Are you getting air through the idle circuit? Plug the idle air inlet on the top of the carb and see if the idle falls.

Next you can't sync the carbs by trying to raise the idle. You need to do it by equalizing the airflow through them with a special gauge or a hose held between the carb throats and your ear.

Lots of posts on both.